U.S. patent application number 13/043813 was filed with the patent office on 2011-09-15 for zoom system for a microscope and method of operating such a zoom system.
This patent application is currently assigned to Leica Microsystems (Schweiz) AG. Invention is credited to Manfred Kuster.
Application Number | 20110222146 13/043813 |
Document ID | / |
Family ID | 44507663 |
Filed Date | 2011-09-15 |
United States Patent
Application |
20110222146 |
Kind Code |
A1 |
Kuster; Manfred |
September 15, 2011 |
Zoom System For A Microscope And Method Of Operating Such A Zoom
System
Abstract
The present invention relates to an afocal zoom system for a
microscope with a shutter for controlling the depth of focus of the
microscopic image produced by an object, wherein at least one
shutter is disposed in front of the first lens group of the zoom
system, viewed from the object, in the direction of the beam path
passing through the zoom system, and/or at least one shutter is
disposed on a lens group of the zoom system the diameter of which
can be varied in order to control the depth of focus, without
causing vignetting of the edge beams.
Inventors: |
Kuster; Manfred; (Widnau,
CH) |
Assignee: |
Leica Microsystems (Schweiz)
AG
Heerbrugg
CH
|
Family ID: |
44507663 |
Appl. No.: |
13/043813 |
Filed: |
March 9, 2011 |
Current U.S.
Class: |
359/380 ;
359/656 |
Current CPC
Class: |
G02B 21/00 20130101;
G02B 27/0075 20130101; G02B 21/025 20130101 |
Class at
Publication: |
359/380 ;
359/656 |
International
Class: |
G02B 21/02 20060101
G02B021/02; G02B 15/14 20060101 G02B015/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 10, 2010 |
DE |
10 2010 002 722.7 |
Claims
1. An afocal zoom system for a microscope comprising: a plurality
of lens groups including a first lens group determined in the
direction of a beam path passing through the zoom system from an
object; and a first shutter having a variable diameter opening for
controlling a depth of focus of a microscopic image of the object,
wherein the first shutter is fixedly disposed in front of the first
lens group or is disposed on a lens group in the plurality of lens
groups.
2. The afocal zoom system according to claim 1, wherein the first
shutter is arranged immediately in front of the first lens
group.
3. The afocal zoom system according to claim 1, wherein the
plurality of lens groups includes a movable lens group, and the
first shutter is mounted on the movable lens group.
4. The afocal zoom system according to claim 3, wherein the first
shutter is an opto-electronic shutter.
5. The afocal zoom system according to claim 1, wherein the
plurality of lens groups includes a last lens group determined in
the direction of a beam path passing through the zoom system from
an object, and the afocal zoom system further comprises a second
shutter arranged after the last lens group.
6. The afocal zoom according to claim 5, wherein the second shutter
is arranged immediately after the last lens group.
7. A microscope comprising an afocal zoom system, the afocal zoom
system having a plurality of lens groups including a first lens
group determined in the direction of a beam path passing through
the zoom system from an object and a first shutter having a
variable diameter opening for controlling a depth of focus of a
microscopic image of the object, wherein the first shutter is
fixedly disposed in front of the first lens group or is disposed on
a lens group in the plurality of lens groups, whereby the depth of
focus of the microscopic image is adjustable as a function of a
selected magnification of the zoom system.
8. A method of operating an afocal zoom system of a microscope for
imaging an object, the afocal zoom system having a plurality of
lens groups including a first lens group determined in the
direction of a beam path passing through the zoom system from an
object, a last lens group through which the beam path passes, a
first shutter fixedly disposed in front of the first lens group or
disposed on a lens group in the plurality of lens groups wherein
the first shutter has a variable diameter opening, and a second
shutter disposed after the last lens group of the afocal zoom
system wherein the second shutter has a variable diameter opening,
the method comprising the steps of: adjusting a magnification of
the afocal zoom system; varying the diameter of the second shutter
opening to control a depth of focus of the object image at low to
medium magnifications of the afocal zoom system; and varying the
diameter of the first shutter opening to control the depth of focus
of the object image at medium to high magnifications of the afocal
zoom system.
9. The method according to claim 8, further comprising the steps
of: adjusting the magnification of the afocal zoom system from a
low magnification to a high magnification; increasing the diameter
of the second shutter opening during the adjustment of the afocal
zoom system from low to high magnification such that a brightness
of the object image remains substantially constant; and decreasing
the diameter of the first shutter opening such that the depth of
focus of the object image remains substantially constant.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a zoom system, particularly
an afocal zoom system, for a microscope, particularly an operating
microscope, and an (operating) microscope of this kind, and a
method of operating such a zoom system.
BACKGROUND OF THE INVENTION
[0002] Zoom systems for microscopes, particularly for operating
microscopes or high performance stereomicroscopes, are known in a
number of forms from the prior art. For example, U.S. Pat. No.
6,816,321 discloses an afocal zoom system for high performance
stereomicroscopes with which zoom factors z (ratio of maximum to
minimum zoom magnification) of more than 15 can be achieved.
Besides optional add-on modules, stereomicroscopes of this type
comprise a main objective which images the object towards infinity,
two parallel refractors downstream thereof, for varying the
magnification, and two eyepiece units (binocular tubes) comprising
a tube lens, a reversing system and an eyepiece for optical viewing
with both eyes. The refractors may be in the form of Galileo
refractors for stepwise selection of the magnification or as afocal
zoom systems for continuously selecting the magnification. The
distance of the refractor axis is termed the stereo base. The
numerical aperture of this microscope is half the diameter of the
entrance pupil of the telescope or refractor divided by the focal
length of the main objective.
[0003] German patent DE 102 25 192 B4 relates to an objective for
stereomicroscopes of the telescope type and a corresponding
stereomicroscope. For details of its construction and mode of
operation and the relation between magnification, resolution and
vignetting, reference is made expressly to the above patent.
[0004] A high powered stereomicroscope with enhanced resolution and
at the same time increased depth of focus for the same size of
stereomicroscope is known from German patent DE 10 2006 036 300 B4.
The embodiments in conjunction with FIGS. 9 and 10 in the
specification of that document describe the construction and mode
of operation of the afocal zoom systems used for the high powered
stereomicroscope described therein. To this extent, reference is
made specifically to this specification. Additionally, the afocal
zoom systems referred to are also described in U.S. Pat. No.
6,816,321 mentioned previously (corresponding to DE 102 22 041 B4).
FIG. 1 of the specification of DE 10 2006 036 300 B4 shows two
parallel afocal zoom systems of a stereomicroscope in which an
(iris) shutter or (iris) diaphragm with an adjustable diameter is
arranged within the zoom system. The diameters are adjusted to be
the same for both zoom systems. The iris shutters limit the
corresponding diameters of the entrance pupils which are variably
large, depending on the zoom setting and choice of shutter, but are
the same on both sides.
[0005] In another type of zoom system, an (aperture) shutter or
(aperture) diaphragm is positioned after the last lens component in
the direction of light flow. A corresponding system is
schematically shown in FIGS. 1 and 2 of this application. The zoom
system here is designated 1 and has four lens components or groups
L1, L2, L3 and L4, the two outer lens components L1 and L4 being
fixed, while the two inner lens components L2 and L3 are arranged
to be axially moveable (along the optical axis). The movement of
the lens components L2 and L3 takes place along precisely
prescribed pathways and passes from a setting for low
magnifications (FIG. 1) to a setting for high magnifications (FIG.
2). The shutter (or diaphragm) arranged after the zoom system 1 in
the direction of propagation of the beam is designated B.
[0006] FIGS. 1 and 2 of this application show that the shutter (or
diaphragm) B is effective at low magnifications while it has little
or no effect at high magnifications. The shutter B thus influences
the numerical aperture and hence also the depth of focus and
brightness only for low to medium magnifications, while the depth
of focus at high magnifications, in particular, cannot be
increased. Further closing of the shutter B results in strong
vignetting for the edge regions of the object field. On the other
hand, at low magnification, the depth of focus is great in any
case, so that a further increase in the depth of focus using the
shutter B is scarcely necessary in practice. Further remarks on
this zoom system 1 and on zoom systems in general can be found in
the "Selected Papers on Zoom Lenses", published by Allen Mann, SPIE
Milestone Series, Volume MS 85.
SUMMARY OF THE INVENTION
[0007] An object underlying the present invention is therefore to
provide a zoom system in which the depth of focus can be
influenced, if possible without the disadvantages described above,
even at high magnifications.
[0008] The afocal zoom system according to the invention for a
microscope, particularly an operating microscope, comprises a
shutter (or diaphragm) for controlling the depth of focus of the
microscopic image generated from an object. At least one shutter is
fixedly disposed in front of the first lens group of the zoom
system, viewed from the object, in the direction of the beam path
passing through the zoom system, and/or at least one shutter is
disposed on a lens group of the zoom system the diameter of which
can be varied in order to control the depth of focus. The first
lens group of the zoom system, viewed from the object, is the first
lens group of the zoom system struck by the imaging beam path.
[0009] The zoom system according to the invention is thus
characterised first of all in that, by contrast with the known zoom
systems, the shutter for controlling the depth of focus is not
arranged after the lens groups of the zoom system, in the direction
of the imaging beam path, but in front of it. Because of the
already relatively high depth of focus at low zoom magnifications,
the influence of the "rear" shutter, i.e. the shutter known from
the prior art, on the depth of focus tends to be slight. Moreover,
this rear shutter loses effect at high zoom magnifications or leads
to strong vignetting in this case. If on the other hand instead of
the known rear shutter the front stationary of fixed shutter
according to the invention is used, i.e. a shutter arranged in
front of the first lens group of the zoom system on the light entry
side, this may cut the pencil of rays (pencil of light) equally on
the entrance side, in the range of medium to high zoom
magnifications (cf also FIG. 2) and thus increase the depth of
focus without producing vignetting for the edge regions of the
object field. The fixed front shutter used according to the
invention, in fact, uniformly cuts a pencil of light from the
centre of the object and a pencil of light from a point on the edge
of the object. These pencils of light have the same diameter and
the same position, in fact, at the site of the first lens group,
whereas at the site of the last lens group they still have the same
diameter but are offset from one another. Meanwhile, the front
shutter shows little effect in the range from small to medium zoom
magnifications, which is of no consequence in practice because of
the depth of focus being higher in this range in any case.
[0010] It is particularly advantageous if the said shutter is
constructed as an iris shutter (iris diaphragm). The shutter acts
in a similar manner to an aperture shutter, i.e. it increases the
depth of focus as the shutter diameter becomes smaller, while it
increases the resolution of the image and its brightness as the
shutter diameter increases.
[0011] It is particularly advantageous if the front shutter is
arranged immediately in front of the first lens group of the zoom
system, the term "immediately" referring to an area which begins in
the axial direction at the outermost apex of the first lens group
on the beam entry side and advantageously extends at most to half
the diameter of this first lens group in the axial direction.
[0012] In an advantageous embodiment, a further (second) shutter is
fixedly arranged in the direction of the beam path passing through
the zoom system, after the last lens group of the zoom system,
viewed from the object, i.e. at the exit end of the imaging beam
path of the zoom system itself. This additional shutter corresponds
to the "rear" shutter as known from the prior art. This rear
shutter is, in particular, also arranged immediately after the last
lens group, the term "immediately" referring to an area which
begins at the outermost apex of the last lens group of the zoom
system on the beam exit side and advantageously extends in the
axial direction to half the diameter of this last lens group.
[0013] Whereas the first, front shutter is used primarily to
regulate or adjust the depth of focus in the range from medium to
high zoom magnifications, the second, rear shutter may be used to
regulate or adjust the depth of focus and/or brightness at low to
medium zoom magnifications.
[0014] This arrangement makes it possible to carry out a method
described hereinafter for operating the zoom system according to
the invention.
[0015] In another aspect of the invention, alternatively or
additionally, at least one shutter is arranged on a lens group of
the zoom system, the diameter of which can be varied in order to
control the depth of focus. A shutter of this kind is, in
particular, an opto-electronic element such as an LCD (liquid
crystal display). Particularly suitable are elements of this kind
in film form which can be applied directly to a lens group of the
zoom system, whilst it should also be understood that elements of
this kind may be applied to individual lenses of a lens group.
[0016] In another advantageous embodiment of this second aspect of
the invention the said shutter may be mounted in particular on a
moveable lens group of the zoom system. In a zoom system the site
of the aperture varies depending on the zoom magnification
selected. The magnification of the zoom is set by a defined
movement of at least one lens group of the zoom system, so that
mounting the shutter on a suitable moveable lens group may have the
effect of ensuring that the shutter is always as close as possible
to the site of the aperture.
[0017] The shutter proposed according to the second aspect of the
invention and mounted on a lens group of the zoom system may in
particular replace the front and/or rear shutter described
according to the first aspect of the invention: for example,
instead of the front shutter (according to the first aspect) a
shutter (according to the second aspect) may be provided on the
first lens group of the zoom system. Conversely, instead of the
rear shutter (according to the first aspect) a shutter (according
to the second aspect) may be mounted on the last lens group of the
zoom system. Furthermore, in a four-component zoom system, for
example, instead of a front shutter (according to the first
aspect), a shutter (according to the second aspect) may be mounted
on the second lens group of the zoom system and/or instead of the
rear shutter (according to the first aspect) a shutter (according
to the second aspect) may be mounted on the third (penultimate)
lens group of the zoom system. Further permutations of the above
combinations are possible and will be apparent to the skilled man
without departing from the scope of the present invention. These
permutations are to be regarded as having been expressly disclosed
without each individual permutation requiring detailed
explanation.
[0018] The invention further relates to a microscope, particularly
an operating microscope, with an afocal zoom system according to
the invention as described above for imaging an object with a
variable depth of focus. Microscopes of this kind, particularly
stereomicroscopes and operating microscopes, are known per se in
their construction and mode of operation (cf. the prior art
mentioned in the introduction to the description).
Stereomicroscopes of the telescope type have a main objective
common to both beam paths, adjoining which in the axial directions
are two zoom systems. These are in turn connected to two eyepiece
units, each comprising tube lenses which generate immediate images,
and symmetrical reversing systems for rectifying the image, and
finally two eyepieces. In this case the user perceives the
three-dimensional image of the object directly with his eyes.
Optionally, in known manner, additional assemblies may be provided
in the beam path, such as for example lens attachments, filters,
polarisers, illuminating units, beam splitter systems for coupling
in and out of light, etc. Regarding microscopes of this kind
reference is expressly made once again to DE 10 2006 036 300
B4.
[0019] The invention further relates to a method of operating an
afocal zoom system according to the invention for imaging an object
by means of a microscope, particularly an operating microscope, the
zoom system having a first shutter and a second shutter, the first
shutter being arranged in front of the first lens group of the zoom
system, in the direction of the beam path passing through the zoom
system, viewed from the object, and the second shutter being
arranged after the last lens group of the zoom system, and the
depth of focus of the image being controlled by varying the shutter
diameter of the second shutter, for small to medium magnifications
of the zoom system, and by varying the shutter diameter of the
first shutter, for medium to high magnifications of the zoom
system. Thus, using the method according to the invention, it is
possible to adjust the depth of focus over the entire range of
magnifications of the zoom system without at the same time getting
strong vignetting for the edge regions of the object field during
the transition to high magnifications. Regarding the mode of
operation of this method reference should be made to the above
remarks in connection with the zoom system according to the
invention, particularly the embodiment with a first, front, and
second, rear, shutter.
[0020] In one particular embodiment of the method according to the
invention, the said shutters may optimally be used to control
brightness and depth of focus while zooming through the range of
magnifications of the zoom system: for this purpose, during the
transition from small to high zoom magnifications, for example, the
shutter diameter of the second, rear, shutter is increased such
that the brightness of the imaging remains as constant as possible.
As it is known that the brightness of an image decreases as the
zoom magnification increases, this effect can thus be compensated
by having the diameter of the second, rear, shutter increased
accordingly. On the other hand, during the transition from low to
high magnifications of the zoom system, the shutter diameter of the
first, front, shutter may be reduced in size so that the sharp
reduction in the depth of focus is mitigated. As the depth of focus
of the image decreases sharply as the zoom magnification increases,
this effect can thus be attenuated by reducing the size of the
shutter diameter of the first, front, shutter accordingly.
[0021] As in this embodiment a change in the shutter diameter of
the first, front, shutter also affects the brightness of the image
and conversely a change in the shutter diameter of the second,
rear, shutter also affects the depth of focus of the image, it is
expedient to use a software-based control or regulating method in
order that, for example, the brightness be kept as constant as
possible over the entire zoom range.
[0022] It makes sense to adopt the following values for the terms
"low," "medium," and "high magnification" (magnification factor):
The range for low magnification is from 0% to 25%, the range for
medium magnification is from 25% to 75% and the range for high
magnification is from 75% to 100% of the maximum zoom magnification
that can be achieved.
[0023] For the method according to the invention as described,
regarding the alternative or additional use of a shutter mounted on
a lens group, the remarks made above in connection with the zoom
system according to the invention also apply. To avoid repetition,
reference is made thereto. In particular, in this method, the first
shutter (front shutter according to the first aspect of the
invention) may be replaced by a shutter which is mounted on the
first lens group of the zoom system or (more advantageously) on a
movable lens group of the zoom system located behind it. In another
embodiment it is also possible to replace the second shutter (rear
shutter according to the first aspect of the invention) by a
shutter according to the second aspect of the invention. The latter
shutter is mounted in particular on the last lens group of the zoom
system or (more preferably) on a movable lens group of the system
located in front of it. With regard to the procedure used in the
method and possible options and advantages arising therefrom,
reference is made specifically to the earlier comments.
[0024] It will be understood that the features mentioned above and
those about to be described hereinafter may be used not only in the
particular combination specified, but also in other combinations or
on their own, without departing from the scope of the present
invention.
[0025] The invention is illustrated by an embodiment shown
schematically in the drawings and is described in detail
hereinafter with reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Further preferred embodiments are indicated in the subclaims
and will be described below in more detail with reference to the
drawings, in which:
[0027] FIG. 1 shows a zoom system according to the prior art with
the pencil of light of the imaging beam path for low zoom
magnifications;
[0028] FIG. 2 shows a zoom system according to the prior art with a
pencil of light of the imaging beam path for high zoom
magnifications;
[0029] FIG. 3 shows a zoom system according to the prior art with a
pencil of light of an edge beam in medium to high zoom
magnifications;
[0030] FIG. 4 shows an embodiment of a zoom system according to the
invention with a pencil of light of the imaging beam path for
medium to high magnifications; and
[0031] FIG. 5 diagrammatically shows a stereomicroscope with a zoom
system in an embodiment according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0032] FIG. 1 shows, in a highly schematic view, a zoom system 1 of
the kind known from the prior art cited in the introduction to the
description. The zoom system 1 consists of four lens groups L1 to
L4, the two outer lens groups L1 and L4 being fixed and the two
inner lens groups L2 and L3 being arranged so as to be axially
movable. Whereas FIG. 1 shows a setting of the inner lens groups L2
and L3 for low magnifications, FIG. 2 shows a setting for high
magnifications. Each lens group L1, L2, L3, L4 consists of a
plurality of individual lenses which may be cemented together.
Since, in the arrangement of the lens groups L1 to L4 shown and in
view of the fact that they have to be moved, an (aperture) shutter
or diaphragm can only be fitted by increasing the construction
volume and/or by reducing the zoom range that can be achieved, it
is common to place a shutter B, which is usually in the form of an
iris shutter, behind the last lens group L4 in the direction of
beam propagation.
[0033] As shown in FIG. 1, at low magnifications the shutter B has
the effect of limiting the pencil of light emerging from the last
lens group L4. Because of the high depth of focus that is already
present at low magnifications, however, this measure tends to
affect the brightness and the resolution of the image rather than
the depth of focus.
[0034] As is apparent from FIG. 2, at high magnifications the
shutter B does not affect the diameter of the pencil of light
emerging from the last lens group L4 for the axis point and object
points close to the axis. It is indeed possible to reduce the
diameter of the shutter B still further, at high magnifications, in
order to increase the depth of focus, but because of the strong
vignetting for the edge beams (cf. FIG. 3) this involves a
considerable loss of quality of the image.
[0035] FIG. 3 shows a known afocal zoom system 1 with four lens
groups L1 to L4 with the beam pencil of an edge beam, i.e. an
object point remote from the axis. The beams entering the zoom
system 1 and the beams leaving the zoom system 1 are all parallel
to one another (afocal zoom system). A comparison of FIG. 3 with
FIG. 2 clearly shows that the pencil of light of an edge beam is
offset on the exit side of the zoom system 1 relative to the pencil
of light for the axis point. This explains the previously mentioned
strong vignetting for the edge beams when a shutter is provided on
the exit side of the zoom system 1.
[0036] FIG. 4 shows, starting from the zoom system according to
FIGS. 1 and 2, a particularly preferred embodiment of a zoom
system. Here, a first, fixed front shutter B2 is arranged in front
of the first lens group L1 of the zoom system 1. Moreover, a
second, fixed rear shutter B1 is arranged behind the last lens
group L4.
[0037] First of all, the mode of operation of the first, front
shutter B2 will be discussed. For this purpose, the shutter B1 can
be regarded as not being there. At the medium to high magnification
of the zoom system 1 shown, the shutter B2 leads to a uniform
cutting of the pencil of light entering the zoom system, i.e. both
the pencil of light from the centre of the object and that of the
edge beam (cf. FIG. 3). A reduction in the shutter diameter of the
shutter B2 thus leads to an increase in the depth of focus, without
causing vignetting for the edge regions of the object field. With
regard to the situation at low to medium magnification, it can be
stated, with reference to FIG. 1, that the shutter B2 has little
influence because of the reduced cross-section of the pencil of
light in the direction of low magnification. As already mentioned
several times, however, this is of no significance in practice, as
there is in any case a high depth of focus in this magnification
range.
[0038] Particular possibilities are opened up by combining the
first, front shutter B2 with the rear shutter B1, already discussed
with reference to FIGS. 1 and 2, which is also referred to here as
the second shutter B1. With an arrangement of this kind, the depth
of focus and the brightness can be optimally adjusted while at the
same time vignetting is kept to a minimum over the entire zoom
range. The second, rear shutter B1 may be used to adjust the
optimum brightness, in particular at low to medium zoom
magnifications, while for medium to high zoom magnifications the
first, front shutter B2 should be used for optimum adjustment of
the depth of focus.
[0039] The adjustment of the two shutters B1 and B2 may be matched
to one another in particular so that, during a transition from low
to high zoom magnification, the brightness of the image is
essentially kept constant by the fact that the diameter of the
second, rear shutter B1 is enlarged. The optimum selection of the
depth of focus can then be carried out by adjusting the shutter B2,
the latter being reduced in diameter to keep the depth of focus
constant during the transition from a low to a high zoom
magnification. As a reduction in the diameter of the shutter B2
also affects the brightness of the image, this effect has to be
taken into consideration when correspondingly adjusting the shutter
B1 to keep the brightness constant. Obviously, the reverse also
applies, as a change to the shutter B1 results in an effect,
however small, on the depth of focus, which is what is supposed to
be controlled primarily by the shutter B1 in this embodiment.
[0040] With the arrangement of the two shutters B1 and B2 shown in
FIG. 4, a software-based control or regulation can be carried out
particularly to adjust the brightness and depth of focus in the
imaging of an object using a microscope having a zoom system 1 as
shown in FIG. 4. A control unit 11 is preferably used which records
the respective positions of the movable lens groups L2 and L3 as
its input variables. The respective positions of these lens groups
L2 and L3 are a measurement of the zoom magnification selected.
Depending on this, the control unit 11 delivers output variables
for adjusting the shutters B1 and B2 in their respective
diameters.
[0041] Although FIG. 4 shows only an embodiment according to the
first aspect of the invention, the skilled man, with his knowledge
gained from the description of the invention according to the
second aspect, will easily be able to replace one of the shutters
B1 or B2 or both shutters B1 and B2 with the corresponding shutter
or shutters according to the second aspect of the invention. No
detailed description will be provided at this point, in the
interests of conciseness.
[0042] FIG. 5 schematically shows a stereomicroscope having a zoom
system according to an embodiment of the invention. The
stereomicroscope of the telescope type enables the viewer, whose
eyes are designated 8R and 8L, to obtain a three-dimensional
impression of the object 3 being viewed. For this purpose, the
object 3, which is located in the front focal point of the
objective 2, is imaged through two separate optical channels. The
two viewing channels 10L and 10R are of similar construction and
each contain a zoom system 1L, 1R, a tube lens 4L, 4R and an
eyepiece 7L, 7R. Image reversal systems 5L, 5R arranged behind the
tube lenses 4L and 4R provide intermediate images 6L, 6R that are
the right way up, which are viewed visually using the pair of
identical eyepieces. The pairs of optical elements mentioned above
are arranged parallel and symmetrically with respect to the axis 9
of the objective 2. The two zoom systems 1L, 1R selectively change
the magnification, but in the same way for the left- and right-hand
channels 10L, 10R.
[0043] The two intermediate images 6L and 6R are different images
of the object 3, as the object 3 is viewed in the left-hand channel
10L at the angle wL and in the right-hand channel 10R at the angle
wR. In this way it is possible to achieve a stereoscopic view of
the object 3.
[0044] The axis point of the object 3 is designated OM, while
points remote from the axis are designated OU or OO, from which
edge beams proceed (cf. FIG. 3). EP denotes the diameter of the
entrance pupil of the zoom systems 1L, 1R. The references uL and uR
denote the half-angles of opening of the cone with its vertex in
the centre of the object OM, which is bounded by the entrance
pupil.
[0045] At the maximum magnification of the zoom systems 1L, 1R, the
entrance pupil diameter EP is at its maximum (cf. FIG. 2) and is
then designated ENP. The object width, i.e. the spacing of the
object 1 from the first surface of the objective 2, is designated
OW. The field angle W shown in FIG. 5 turns out to be comparatively
large, as a result of the object width OW which is chosen here to
be small. Further explanations of the stereomicroscope shown can be
found in DE 102 25 192 B4.
[0046] In FIG. 5, each of the zoom systems 1R and 1L is made up of
the same four lens groups L1, L2, L3 and L4. According to the
second aspect of the invention described, an opto-electronic
shutter B3 is mounted on the second lens group L2. The shutter B3
is thus located on a movable lens group and is thus better able to
take over the function of an aperture shutter. As already described
in connection with FIG. 4, it is advantageous to provide another
shutter towards the beam exit end, i.e. in this instance another
shutter in the direction of the beam exit end of the zoom systems
1L and 1R. This additional shutter may also be an opto-electronic
shutter which is preferably mounted on the lens group L3 or on the
lens group L4. Finally, a conventional shutter may also be arranged
immediately after the lens group L4 (cf. B1 in FIG. 4).
[0047] Instead of the electro-optical shutter B3 shown, which is
mounted on the lens group L2, each of the zoom systems 1R and 1L
may be replaced by a zoom system shown in FIG. 4. By this means,
also, a microscope is obtained, particularly an operating
microscope, with which it is possible to control the brightness
and/or depth of focus of the image, as described. For controlling
the shutters of the respective zoom systems 1L and 1R, a single
control unit 11 is sufficient, which controls the corresponding
shutters jointly, and moreover the position of the movable lens
groups of a zoom system (1L or 1R) are sufficient as input signals
for the control unit 11, as the two zoom systems 1L, 1R must always
have the same zoom magnification.
LIST OF REFERENCE NUMERALS
[0048] 1, 1R, 1L Zoom system [0049] 2 Objective [0050] 3 Object
[0051] 4R, 4L Tube lens [0052] 5R, 5L Image reversal system [0053]
6R, 6L Intermediate image [0054] 7R, 7L Eyepiece [0055] 8R, 8L Eye
[0056] 9 Axis of the objective [0057] 10R, 10L Viewing channel
[0058] 11 Control unit [0059] B Shutter [0060] B1 Second shutter
[0061] B2 First shutter [0062] B3 Opto-electronic shutter [0063] EP
Diameter of the entrance pupil [0064] L1-L4 Lens groups [0065] OM,
OU, OO Object point [0066] OW Width of object [0067] uR, uL
Half-angles of opening [0068] W Field angle [0069] wR, wL
Observation angles
* * * * *